By the time of that campaign Titus had served for over 150 years. During his youth he struggled with his temper. During one campaign against the forces of Chaos he was badly injured slaying a Chaos Sorcerer who wiped out the rest of his squad. The aftermath of that action led some to question how Titus survived where the rest of his battle brothers had fallen.
Titus's company commander was his mentor and Titus was by his side when he fell in battle. Titus was then promoted to take his place and has felt the weight of command ever since.
While walking through the Hall of Heroes on Macragge, Captain Sicarius observed the statues of fallen Ultramarines. One of them was of a Captain Titus. This could be a simple way of implying that Titus died at some point, leaving command of Second Company to Sicarius. 
- Titus is the player's character for the game, Warhammer 40,000: Space Marine.
- Titus may have been one of the Captains of the second company, judging by the colours on the shoulder plate rims.