Massachusetts State Police/AP Photo

Investigators are searching for a motive behind the alleged shooting of one Massachusetts police officer by another, who then fatally shot himself, according to police.

The two men knew each other and had arranged to meet at a Starbucks coffee shop at a strip mall, according to investigators, who have not said if a motive for the shooting has been established.

Beverly police officer Jason Lantych, 35, stumbled into the Starbucks around 6 p.m. He had been shot in the in his groin and wrist and was bleeding profusely. Patrons immediately came to his aid.

Witnesses told police they heard multiple gunshots right before Lantych entered the coffee shop. Lantych identified the gunman as Sgt. Kenneth Nagy, 43, who allegedly fled the scene in a black SUV.  Nagy was an off-duty sergeant from a nearby town, Hamilton.

"He was shot in the groin area," one man told ABC News affiliate WCVB. "We elevated his leg and applied pressure and I told my buddy to apply pressure, we got the bleeding to slow down a little bit."

Lantych was rushed to the hospital and underwent surgery Friday night. Police told WCVB he was listed in critical condition.

Police credit good Samaritans for saving Lantych's life, including nurse, Deborah Crosbie, and medical student, John Sholomith.

"It was more of an instinct thing for me to get up and run," said Sholomith, according to WCVB. "I elevated his leg and applied pressure."

Saturday, some of Nagy's neighbors were in complete shock over the incident. They painted him as a man who loved his wife and two young sons.

"I would see him (Nagy) at baseball practice or tryouts and basketball as well and it's just tragic," a neighbor named Rob told WCVB. "That's the only thing."

Manhunt Launched for Nagy Before Suspected Suicide

Friday night, investigators identified Nagy as the prime suspect in the shooting. A warrant for his arrest was issued and a statewide manhunt was launched.

Essex County District Attorney Jonathan Blodgett warned the public during a press conference Friday night that Nagy was armed and dangerous.

"We believe he shot him and we want the public's assistance. Give us information if they see him, but do not approach him," Blodgett said.

Just 15 minutes after the plea from the district attorney, the search was over.

Nagy pulled into a parking lot on the opposite side of the building from where the mayhem began.

Blodgett told WCVB that state troopers and Beverly police officers cordoned off the area. Investigators did not immediately see Nagy leaned back in the driver's seat. They searched the parking lots and the railroad tracks before approaching the vehicle.

As officers made their move towards Nagy's SUV, he fatally shot himself.

A report from the Hamilton-Wenham Chronicle indicates that Nagy had been promoted to the rank of sergeant last July.

A picture shows his wife, Katie, placing an honorary pin on her husband. Other photos show the couple smiling with their two children, Gavin and Griffin.

The Massachusetts State Police told ABC News that they will not make any further comments on the case and that it's being handled by the Essex County District Attorney's Office.

ABC News attempted to reach the DA's office but has not received any response.