Piermont, New York (CNN) -- Autopsy results were released on Monday for a bride-to-be and best man who were killed in a boating accident last weekend on the Hudson River.
Lindsey Stewart died "as a result of drowning and severe head injuries" and Mark Lennon died "as a result of drowning" and "suffered only minor bodily injuries," according to a press release from the Rockland County Medical Examiner's office.
Lennon and Stewart disappeared late Friday when a 21-foot Stingray power boat they were passengers on slammed into one of three construction barges strapped together near the Tappan Zee Bridge, 25 miles north of Manhattan. Lennon was to be the best man in Stewart's wedding to Brian Bond on August 10.
Both deaths are being certified as "vehicular homicide," according to the release.
Post mortem toxicology tests for drugs and alcohol are pending and expected to take several weeks for completion, the release says.
Stewart and Lennon were thrown from the boat.
Stewart's body was recovered Saturday. But the search for Lennon continued until Sunday morning, when a Jet Skier called police to report a body in the river.
"We're looking into every single thing," Rockland County, New York, Sheriff Louis Falco said. "What we're going to do is bring in an accident reconstruction team."
It was supposed to be a short boat ride up the Hudson River from the village of Piermont in Rockland County to Tarrytown
The couple had just dined at a restaurant with friends when Stewart and Bond boarded the power boat, along with three friends.
Potential alcohol use and poor lighting are key points of interest as authorities look into the deadly crash.
The barge the power boat crashed into had been anchored in the river since April, according to Robert Van Cura, undersheriff of the Rockland County Sheriff's Office.
"The barge had some lights on it; whether or not it was properly lighted is part of the investigation," Van Cura said.
"On a clear, moonlit night, with the bridge lights on, you can see pretty well," said Tom Sobolik in a telephone interview from aboard his sailboat near the accident site.
The moon was last full on Monday.
But Craig and Celeste Kmiecik said they were boating in the area Friday night, and it was dark.
"There was a moon last night, but you really can't see anything," said Craig Kmiecik.
"The barge was not lit up," said Celeste Kmiecik. "We saw that last night coming back to the marina."
Another area resident, Anthony Fowler, said having barges on the waterway is dangerous.
"If you put an immovable object that's dark in the path of recreational boaters, you have a recipe for disaster."
Meanwhile, boat operator Jojo K. John, 35, has been arrested.
"We have probable cause to believe that he operated the boat while intoxicated," Van Cura said.
John was arraigned at an area hospital on one count of first-degree vehicular manslaughter and three counts of second-degree vehicular assault. More charges are possible, Van Cura said.
John, along with the others who were not thrown from the boat, suffered head injuries.
Bond, the groom, was hospitalized at Westchester Medical Center, said Stewart's stepfather Walter Kosik, who visited him Saturday. "He was in no condition to talk."
A spokesman for the medical center said Bond was in fair condition, with serious head injuries. He was the one who called 911 from the boat, reporting the accident.
For the families, the tragedy was magnified by the pending nuptials.
"She's supposed to be married two weeks from today," said Carol Stewart about her daughter. "It just can't end like this."
CNN's Chris Welch, Alan Duke, Rande Iaboni, and Tom Watkins contributed to this report.