While celebrating Kellar's 21st birthday and the birthday of Rodgers' wife, the ADA told the court that Kellar and his sister became involved in a verbal altercation.
Kellar left the hotel room with his belongings but later returned to retrieve additional items shortly before 11:30 p.m., prosecutors said in court, at which point the altercation continued and Kellar began pushing his sister.
At that point, Rodgers is accused of stabbing the unarmed Kellar in the back with a knife.
Kellar was taken to a local hospital where he was pronounced dead. Prosecutors said Rodgers remained at the hotel until Boston police officers arrived.