Former NFL wide receiver Vincent Jackson likely died several days before he was confirmed dead in his Tampa-area hotel room, according to multiple reports Thursday night.

Jackson, 38, was found dead Monday in his room at the Homewood Suites in Brandon, Fla. A cause of death has not been released.

ESPN and TMZ Sports obtained a death report from the Hillsborough County Sheriff’s Office. The report noted that hotel staff entered the room on Saturday and Sunday but left after seeing Jackson slouched over on the couch and assuming he was asleep.

By Monday, after seeing Jackson in the same position, hotel staff called 911.

Jackson had been staying at the hotel since Jan. 11, according to ESPN. His family filed a missing-persons report Feb. 11, and deputies located him at the hotel Feb. 12 and spoke with him. The missing-persons case was canceled, and deputies deemed Jackson fit to stay at the hotel.

Both ESPN and TMZ noted that the death report mentioned Jackson having a history of alcohol use and smokeless tobacco use. The report said Jackson was not a known drug user.

Also Thursday, the New York Times first reported that Jackson’s family had donated his brain to Boston University’s CTU Center. Scientists will study Jackson’s brain for signs of chronic traumatic encephalopathy, which can be caused by repeated blows to the head.

Jackson played 155 games in an NFL career that spanned 2005-16.