Professor Donald "Donnie" Lonegan is the killer of Dr. Jim Mallory and the identical twin brother of Irish mobster Cally Lonegan.
Background[]
Cally and Donnie both struggled in the same rough neighborhood, with the same drunk, violently abusive father, who Cally took the brutality from to protect Donny. While Cally was a troublemaker running with bad crowds all the way to being the last of the Westies, Donnie was the academic, who Cally supported all their lives to graduate school and become a math professor at Oneida U. Donnie married a woman named Mary and had a daughter, Margaret Sikorsky. If not familiar with the twins or putting them side by side, they uncannily resembled each other, save for Cally looking older than Donnie to his alcoholism and resulting cirrhosis. Cally went into business with Dr. Mallory, but Mallory, a typical womanizer, had a history of possessing woman by getting them addicted to drugs just so he could abuse them. he set his sights on Margaret, who consequentially died from a combined drug overdose.
Brother's Keeper[]
As upset as Donnie was from Cally pulling Margaret into his life, Donnie's heartbreak turned to rage especially directed at Mallory. Donnie checked in at an average hotel not far from Penn Station, where he took the train to Manhattan and was driven to the country club Mallory was at by Sierra Leone-born cabbie Sebastian Waziri. Mallory was later shot in the back of the head with a .22, which wasn't stopped by security guard Art Bilson because he took a nap. Sebastian took Donnie back to the station, then he checked and returned to Oneida, hoping his lie he told his staff covering for him, that he was at his cabin in the Adriondacks, would be a convincing albeit flimsy alibi. Cally was naturally the prime suspect, as Mallory was fleecing him; the motive was strengthened when Margaret's death came to light. However, two FBI agents using Cally as a snitch, Agents Ron Innes and Jeff Washington, put his alibi in Queens, which was ironclad enough for Cally. Then Sebastian was executed the same way, definitely by Cally, as he used the gun to assault enforcer Patrick Delahunt, and nurse Barbara Landers recognized him distinctly due to signs of his drinking.
Cally was arrested on charges of both murders, even after Donnie came into the picture. To protect Donnie, Cally was ready to take a maximum penalty guilty plea. This is when the detectives and prosecution realized Donnie may have killed Mallory, with Cally murdering Sebastian and taking the rap in full to protect Donnie. They later found the hotel Donnie checked into, where he was obligated to show his ID. Agent Innes was found to have tipped off Cally, as they were friends in high school, which resulted in Sebastian's murder. Cally shut Donnie up when the prosecution confronted them, especially to stay steadfastly taking the blame for everything. Donnie wanted to confess, as his crimes got killed a West African national who was working to rescue his family from his war torn home. Cally wouldn't have that, making Donnie understand the mob wouldn't accept a plea as much as the law would, guilty Donnie over how he was the rock who kept Donnie going throughout his life. Donnie kept quiet, and Cally still insisted on negotiating a deal. The D.A.'s office were keeping the investigation hot and open, but Cally was later reported to have been shanked in prison, as a mob-ordered hit in revenge for his informant work.