Joe Kennedy, who was suppose to be a best man at wedding today, has died today. The Toronto Blue Jays pitcher was only 28 years old. No cause of death has been determined thus far, but his agent thinks it was either a heart attack or a brain aneurysm.

Damon Lapa, his agent spoke today saying "The cause of death is unknown at this time," Lapa told FOXSports.com. "The best guess at this point is either a heart attack or a brain aneurysm. The way he died was sudden. There is no reasonable explanation for what happened."

"We were terribly shocked," Blue Jays president Paul Godfrey said. "From what we understand he was in Bradenton ... to be the best man at a wedding today."

The left-handed Kennedy, 28, was 43-61 with a 4.79 ERA in seven seasons with Tampa Bay, Colorado, Oakland, Arizona and Toronto.