Despite being the initial suspect and the first person who came up in the database, he was actually a pawn working in league with Steve Kerwin.
The leads surrounding Grimes' involvement in the various drug-related arrests and having killed a cellmate in what he claimed was "self-defense," Grimes was suddenly set on earlier release with little attention and yet much surprise later on following his death.
When the Federal Bureau of Investigation attacked his hideout and following the deaths of all of his henchmen and a few fellow agents, he ended up being killed in a gunfight with postal inspector Beau Stoddard after refusing to stop avoiding arrest and continuing to open fire at Beau while still injured. Grimes was a stubborn man who claimed he was innocent as all get out in the day's events and later on it was found out by agent Jane Dreyer and Beau that Grimes had been freed earlier by falsified documents by Director of Domestic Security nominee Robert Brickland in league to work with mad man Kerwin since Brickland, who was responsible for helping with Grimes' arrest, knew that he was the type of criminal with experience creating bombs. This wasn't known to Beau or Jane at the time though as they had nothing to go on other then that Grimes was heading to meet a man named Steve Kerwin at the address "5345 7th Street."
Brickland had also helped give schematics on the hockey stadium for Kerwin to later transport bombs he and Grimes had helped create to set them off there. Brickland though was doing it to further his career and later look like the hero of the day as opposed to, what later ended up happening, being arrested along for having helped the two deceased criminals in their quest.