According to this article from EWTN:
Thomas Sherwood was not a priest and he was not a religious. He had planned to study for the priesthood but had not yet carried out his plan when he was arrested.
He was by profession a wool draper and was associated with other Catholic families, in particular the family of Lady Tregonwell. The son of Lady Tregonwell turned him in to the authorities, who sent him to the Tower of London. There he was tortured in order to discover where he heard Mass, who the priest was who celebrated the Mass, and the names of other Catholics with whom he was associated.
St. Thomas More's son-in-law, William Roper, tried to send him money for medicine and food, but the officer at the Tower would not permit money to be spent on anything but clean straw for him to sleep on. Blessed Thomas Sherwood was twenty-seven years old at the time of his arrest, and his brother wrote an account of his sufferings and martyrdom. We also possess the directions given to the lieutenant of the Tower from the privy council, ordering him to obtain information from Thomas Sherwood on the rack. After his execution, his mother was arrested and put in prison, where she died fourteen years later.
During his terrible sufferings, all that he said was: "Lord Jesus, I am not worthy to suffer for thee, much less to receive those rewards which thou hast promised to those who confess thee." Three weeks after his death, his death was recorded in the daybook of Douay College, where he had been expected: "On the first of March, Mr. Lowe returned to us from England bringing news that a youth, by name Thomas Sherwood, had suffered for his confession of the Catholic Faith, not only by imprisonment, but by death itself."
He was executed on February 7, 1578--hung, drawn, and quartered because he denied the Royal Supremacy of Elizabeth I, an act of treason according to the State.