A high-profile shooter, Walsh won numerous tournaments within the FBI and the Marine Corps, as well as nationally, and participated in the 1948 Summer Olympics.

[4] After graduating from Rutgers Law School in 1931,[5] Walsh joined the Federal Bureau of Investigation in 1934, becoming a member of the first cohort of agents permitted to carry firearms.

[4] Later that year, he discovered the body of gangster Baby Face Nelson, who died of injuries sustained in a gun battle with the police in Barrington, Illinois, on November 27, 1934.

The FBI, unaware of Nelson's death, continued a broad search for him, which included several home raids, through the night and into the following day.

A subsequent search of Arthur's apartment revealed information that eventually led to locating other members of the Barker family.

On October 12 of that year, he was with a group of FBI agents who ambushed Brady’s gang at Dakin’s, a Bangor, Maine sporting goods store.

[8] Warned by the store owner that some men was wanting to purchase some Thompson submachine guns and would be returning in a few days to collect them, the FBI believing them to be Brady and his gang decided to set a trap.

As Dalhover was being interrogated, Brady and another gang member, Clarence Lee Shaffer, Jr., emerged from their parked car with guns in their hands.

[12] Walsh remained in the FBI until 1942, when he took a leave to serve with the United States Marine Corps during World War II.

In one incident, he and his comrades were pinned down by a sniper on Okinawa, whom Walsh was able to kill from 90 yards away with a single shot to the torso from a M1911 pistol.

[12] In 1962 Walsh was assigned with the rank of colonel as the Commanding Officer of the Weapons Training Battalion at Quantico, where he remained until his retirement in 1970.

Despite a lack of experience with this type of shooting, Walsh competed in the smallbore rifle event at the National Matches in 1932, and did so well that he was selected as an alternate on the elite Dewar Trophy Team.

In that same year he set a new record in the smallbore national match course at Rumford, Rhode Island, and became the New Jersey State Pistol Champion.

[22] In the late 1970s Walsh took up muzzle loading and black powder shooting, serving as both coach and active shooter on several U.S. international muzzleloading teams.

[1][27] The couple had five children: Walter, Gerald, Kathleen, Rosemary and Linda and by the time of Walsh’s death seventeen grandchildren.