BOSTON — A West Roxbury man was held without bail Monday after he allegedly shot his father to death in the home they shared.

Mark Tomas Regan, 33, was arraigned in West Roxbury Municipal Court in connection with the fatal shooting of Mark Thomas Regan, 66.

Prosecutors allege police found the victim dead at 105 Perham St. on Friday morning after they were called to the home for a wellness check. Officers allegedly found Mark Tomas Regan hiding in the attic.

The investigation revealed that some of the victim’s co-workers, concerned about his absence from work, visited the home on Wednesday. The defendant allegedly told them that he wasn’t home and was out with friends.

Mark Tomas Regan is currently on probation following a two and a half year house of correction sentence on a conviction for unlawful possession of a firearm and assault with a dangerous weapon.