With all eyes on him inside a crowded courtroom, David Desper pleaded guilty Wednesday to fatally shooting Bianca Roberson last June as the two jockeyed for position at a highway lane merger in Chester County.

Desper, 29, seemed flustered, fumbling through his answers to County Court Judge Anne Marie Wheatcraft.

"I'm nervous," he said at one point as his relatives sat stone-faced behind him. On the other side of the aisle, the Roberson family was joined in its silent grief by Bianca's classmates and fellow parishioners at St. Paul's Baptist Church in West Chester.

Desper entered an open guilty plea — meaning there was no agreement on his sentence — to third-degree murder and possessing an instrument of crime, charges that carry a statutory maximum of 40 years in prison. They are a step down from first-degree murder, which Desper initially faced after he turned himself in to West Goshen Township police after a multi-day manhunt.

The plea came five days before Desper's trial was scheduled to begin.

Assistant District Attorney Edwin Miller said the plea came after multiple discussions with Daniel McGarrigle, Desper's attorney, and the Roberson family. They had come to a consensus that one aspect of a first-degree murder charge, malicious intent to kill, would have been difficult to prove.

"After looking at all of the elements of the case … we determined there was a risk that a jury, or even one person on a jury, would say he didn't have that intent," Miller said after Wednesday's hearing. "This decision was not made lightly, and it was made collectively with law enforcement, the district attorney, and the family."

Rodney Roberson, the victim's father, said he accepted that decision after much soul-searching — in recent days, some members of the Roberson family had lashed out on social media about Desper's not facing the harshest charges.

"I just want us to get the full, maximum justice he deserves," Roberson said. "I hope he gets what he deserves, because he had no right to take my daughter's life."

Bianca Roberson's mother, Michelle, could say only that she was hurting.

"I just miss my baby," she added through tears.

Roberson, 18, a recent graduate of Bayard Rustin High School, was returning from a shopping trip in Exton to her family's West Chester home  on June 18, 2017. Authorities said she and Desper were positioning their vehicles at the lane merger, just before Route 202, when Desper fired one shot, striking her in the left side of her head.

Police have said that Roberson had the right-of-way and that Desper was driving recklessly.

After the shooting, Desper fled and left his red Chevrolet Silverado at a friend's house, Miller said during Wednesday's hearing. He then traveled to Delaware as police in Chester County launched a three-day manhunt for Roberson's killer that garnered national attention.

Police documents revealed earlier this year say Desper told a friend about the shooting, saying that he "really f–ed up, man."

After Desper surrendered days later, he turned in his Silverado and consented to a search of his home in Trainer, Delaware County, according to police.

Detectives found gunshot powder residue in his truck as well as rounds, a magazine, and a holster, investigators said at a hearing in March. No bullet holes were found on the vehicle's passenger side and the window was not shattered, which would not be consistent with an accidental discharge. Desper's Smith & Wesson .40-caliber semiautomatic handgun was found in his bedroom. A friend of Desper's previously had said that Desper regularly kept a gun in the truck's center console.

McGarrigle, Desper's attorney, said Wednesday that his client "showed responsibility for this case" by turning himself in and allowing investigators to search his truck and home.

A friend of Desper's told police that Desper said "he didn't know she was a beautiful little girl until the next day when he saw it on the news," according to police documents read in court.

After entering his plea, Desper was returned to the Chester County prison. He is due in front of Wheatcraft in 90 days for sentencing.