Edward Grim's Vita S Thomae is in Late Medieval Books.
Source. Materials for the History of Thomas Becket, Archbishop of Canterbury, James C. Robertson, ed. No. 67, vol. 2 in Rerum Britannicarum Medii Aevi Scriptores. London, 1876.
Translated from Google Translate and The Lives and Legends of the English Saints (pp. 253-256) by William Holden Hutton.
Edward Grim, who witnessed the murder, later wrote an account of the events:
75. Finally, the aforesaid bishops, choosing rather to entrust themselves to the king’s displeasure than to the judgment of God and the Church, quickly crossed the sea and approached the king. Bowing themselves at the king’s feet, they lamented their suspension in a complaint so moving that it might have softened even a hard heart. They explained how the Archbishop of Canterbury had dealt with them, saying that by his contrivance and skill they had been entirely removed from priestly office, to the dishonour of the king and the realm, so that they no longer even had the power to bless the bread. They added, accusing him further, that he would yet dare something greater if the king should patiently endure this presumption. Thus influenced by such words, the king, as if driven out of his senses and beside himself with fury, not knowing what to answer, is reported to have said repeatedly: "I have nourished and raised up in my kingdom idle and wretched men who show no loyalty to their lord, and who allow him to be so shamefully mocked by a certain low-born clerk." Having spoken, he withdrew from the company and sought a private place, perhaps that solitude might give some relief to his conceived anger, where his raging speech might more freely pour forth its venom.
Denique pontifices prajnominati, cum se regis indignationi committere quam Dei judicio et ecclesisæ delegissent, ocius transmisso mari regem adeunt, et se regis inclinantes vestigiis, querula satis et quæ durum licet animum flecteret oratione sua, ipsorum suspensionem deplorant, allegantes qualiter cum ipsis egerit dominus Cantuariensis, cujus industria et ingenio ad regis et regni dedecus a sacerdotali penitus separantur officio, ut nec signandi panem habeant facultatem. Adjiciunt accusantes quod majus aliquid audebit adhuc, si istam rex patienter portaverit præsumptionem. Talibus circumventus rex, et velut amens effectus, nec se capiens præ furore, nescius quid objiceret, hæc iteratis vicibus dixisse fertur: "Inertes ac miseros homines enutrivi et erexi in regno meo, qui nec fidem ferunt domino suo, quern a plebeo quodam clerico tam probrose patiuntur illudi." Dixit, et e medio secedens colloquium pariter et locum familiarem petiit, si quod forte concepto fuiori daret solitudo solatium, ubi liberius sermo ssevientis haustum virus evomeret.
80.....
Whom the butchers pursued, "Absolve", they said, "and restore to communion those whom you have excommunicated, and restore those you have suspended."
To which he answered, "No", he said, "satisfaction is required, I will not absolve them".
"Then you", they said, "will die, receiving what you deserve".
"I", he said, "am ready to die for my Lord, that in my blood the church may obtain liberty and peace; but to my friends, whether cleric or layman, in the name of God Almighty I forbid you to do any harm.
How pious his friends, how wisely for him, provided the excellent martyr, lest the neighbor be injured, the innocent should be overpowered, lest the glory of the one who hastening to Christ would overshadow the sadness of his neighbor!
It was right for the soldier martyr to cling to the footsteps of his Duke's Saviour, who was asked by the ungodly, "If me", he said, "you seek, let these go".
Quem insecuti carnifices, "Absolve," inquiunt, "et communioni restitue quos excommunicasti, et caeteris officium redde qui suspensi sunt."
Quibus ille, "Nulla," ait, "satisfactio praecessit, nec eos absolvam."
"Et tu," inquiunt, "modo morieris, suscipiens quod meruisti."
"Et ego," ait, "pro Domino meo paratus sum mori, ut in meo sanguine ecclesia libertatem consequatur et pacem; sed meis, sive clerico sive laico, in nomine Dei omnipotentis interdico ne in aliquo noceatis.
"Quam pie suis, quam prudenter sibi, providit martyr egregius, ne videlicet laederetur proximus, innocens opprimeretur, ne gloriam properantis ad Christum proximi casus tristior obfuscaret!
Decuit plane Ducis sui militem martyrem Salvatoris inhaerere vestigiis, qui cum quaereretur ab impiis, "Si me," inquit, "quaeritis, sinite hos abire."
81.
Then, making a violent attack, they laid the unholy hands on him, handling and towing him harder, to go outside the church's doors or to slay, or to transport him bound, as afterwards they confessed.
But since he could not move easily from the column, one of them pressed on and go nearer, calling him a pimp, saying, "Don't touch me, Reinarde, you owe me faith by law, and submission; you are acting unwisely with your accomplices".
But the soldier, before the expulsion, glowed with terrible fury, brandishing a sword against the sacred crown, "Unfaithful," he said, "I am not obliged to submit to you contrary to the fidelity of my lord the king".
The indomitable martyr saw the hour that would put an end to his miserable mortality, ready to receive the crown of immortality promised by God, inclined his neck as if praying, joined together and raised up with both hands, to God and St. Mary and to the blessed martyr Dionysius [Denys] he commended his cause and the church.
Igitur facto impetu manus sacrilegas injecerunt in eum, durius illum contrectantes et trahentes, ut extra fores ecclesiae aut jugularent, aut vinctum inde asportarent, sicut postmodum confessi sunt.
Sed cum facilie non posset a columna moveri, unum ex ipsis acrius insistentem et accedentem propius a se repulit, lenonem appellans, dicensque, "Non me contingas, Reinalde, qui fidem ex jure debes et subjectionem; insipienter agis cum tuis complicibus."
Miles vero pro repulsione furore terribili totus incanduit, ensemque vibrans contra sacrum verticem, "Non fidem," ait, "non tibi subjectionem debeo contra fidelitatem domini mei regis."
Cernens igitur martyr invictus horam imminere quae miserae mortalitati finem imponeret, paratam sibi et promissam a Domino coronam immortalitatis jam proximam fieri, inclinata in modum orantis cervice, junctis pariter et elevatis sursum manibus, Deo et sanctae Mariae et beato martyri Dionysio suam et ecclesiae causam commendavit.
82.
Hardly had he said these words, and the fearful and unspeakable soldier lest he should be rescued by the people and escape alive, jumped on him suddenly, and the top of the crown, which the anointing of the holy chrism had dedicated to God, cut off, the lamb of God wounded in the head, and with the same blow cut off the forearm.
In fact, all the fugitives, both monks and clerics, held onto the holy bishop, held in their arms and embraced, until they were also cut.
Behold the simple bird, behold the wisdom of the serpent, in this martyr, who exposed his body to the attackers, and his head, the sould clearly of the church, kept spotless, against the slayers of the body, the more he lacked this necessity, against being ambushed.
O worthy shepherd, who, lest the sheep should be torn in pieces, he poses himself so confidently! and because he had rejected the world, the world willing to crush him unwittingly elevated him.
Then another blow to the head rendered whilst he was still immobile.
The third time the martyr was struck, he bent his knees and elbows, by offering himself a living sacrifice, saying in a low voice, "In the name of Jesus and I am ready to embrace death under the protection of the church."
But the third soldier inflicted a severe wound, with which blow the sword was broken by the stone, the crown, which was large, thus separated from the head, get white blood from the brain, brain still red from blood, lily and rose colors of the virgin, and the face of the confessor's mother and he dyed the martyr's life and death purple.
The fourth soldier drove off the overcoming that the others would commit murder more freely and freely.
The fifth, not a knight, but that clerk who had entered with the knights, not to miss the martyr's fifth stroke, who among others had imitated Christ, putting his foot on the neck of the holy priest and precious martyr, (horrendous to say), spread the brain with blood on the floor, others cried, "Let's go from here, knights, he will not rise further."
Vix verbum implevit, et metuens nefandus miles ne raperetur a populo et vivus evaderet, insiliit in eum subito, et summitate coronae, quam sancti chrismatis unctio dicaverat Deo, abrasa, agnum Deo immolandum vulneravit in capite, eodem ictu praeciso brachio haec referentis.
Is etenim, fugientibus tam monachis quam clericis universis, sancto archiepiscopo constanter adhaesit, et inter ulnas complexum tenuit, donec ipsa quam opposuit praecisa est.
Ecce simplicitatem columbae, ecce serpentis prudentiam, in hoc martyre, qui corpus percutientibus opposuit, ut caput suum, animam scilicet vel ecclesiam, conservaret illaesam [-um?], nec contra carnis occisores, quo magis hac necessitate careret, cautelam vel insidias machinatus est!
O pastorem dignum, qui, ne oves laniarentur, seipsum luporum morsibus tam confidenter opposuit! et quia mundum abjecerat, mundus eum volens opprimere nescius sublimavit.
Deinde alio ictu in capite recepto adhuc quoque permansit immobilis.
Tertio vero percussus martyr genua flexit et cubitos, seipsum hostiam viventem offerendo, dicens submissa voce, "Pro nomine Jesu et ecclesiae tuitione mortem amplecti paratus sum."
At tertius miles ita procumbenti grave vulnus inflixit, quo ictu et gladium collisit lapidi, et coronam, quae ampla fuit, ita a capite separavit, ut sanguis albens ex cerebro, cerebrum nihilominus rubens ex sanguine, lilii et rosae coloribus virginis et matris ecclesiae faciem confessoris et martyris vita et morte purpuraret.
Quartus miles supervenientes abegit ut caeteri liberius ac licentius homicidium perpetrarent.
Quintus vero, non miles, sed clericus ille qui cum militibus intraverat, ne martyri quinta plaga deesset, qui in aliis Christum fuerat imitatus, posito pede super collum sancti sacerdotis et martyris pretiosi, (horrendum dictu,) cerebrum cum sanguine per pavimentum spargens, caeteris exclamavit, "Abeamus hinc, milites, iste ulterius non resurget."