LINCOLN, Neb. --Authorities are investigating a shooting that killed one man on a boat at Branched Oak Lake Tuesday evening. 

The Lancaster County Sheriff's Office said that around 11:30 p.m. deputies arrived to the marina after reports of gunshots and someone yelling for help. 

When they arrived, officials said that they spoke with several people who said the man, 42-year-old Benjamin Case, had been shot. Case was pronounced dead after life-saving measures were attempted. 

LCSO said that life-saving measures were taken by several agencies, including Lincoln Fire and Rescue, Raymond Fire and Rescue and Star Care. 

It was reported that the investigation showed that five people were socializing on Case's Bayliner cuddy cabin boat, moored at the marina. 

Authorities said that an unknown man came onto the boat, when Case had opened the door of the cabin to see who had come on board, he was shot. 

LCSO said that the suspect fled the area in an unknown vehicle. Together LSO and LPD's Crime Scene processed the scene. 

Officials are interviewing other people who were on the boat and also examining video camera footage to gather more information. 

Officers from the Nebraska Game and Parks and Nebraska State Patrol assisted at the scene. 

According to the Sheriff's Office, an autopsy has been scheduled by the Lancaster County Attorney's Office to determine the cause of death. 

Area 11 was closed while the scene was being investigated, but it has since been reopened. 

This is an ongoing investigation. 

Anyone with any information is asked to call the Sheriff's Office at 4020441-6500 or Crimestoppers at 402 475-3600