A Ground Self-Defense Force recruit who fatally shot two of his instructors and injured another during a live-fire training exercise in central Japan last month was served a fresh arrest warrant on Tuesday on suspicion of murder, the Defense Ministry has said.

The 18-year-old recruit is suspected of murdering Yasuchika Kikumatsu, 52, during the exercise at an indoor firing range in Gifu Prefecture on June 14 that involved about 120 personnel, including some 70 recruits.

The recruit shot Kikumatsu in the head and then proceeded to shoot him in the back after he had fallen face-down, according to investigative sources.

Kosuke Yashiro and Yusuke Hara, both 25, were also shot when they tried to stop the recruit from firing at Kikumatsu. Yashiro was killed in the incident, while Hara was wounded in his left leg and will need three months to recover.

The recruit was first arrested for the alleged murder of Yashiro and was quoted as telling investigators he "tried to lower the gunpoint to aim at (Yashiro's) legs but ended up hitting him in the side."

He also revealed he had intended to get ahold of GSDF ammunition, they said.

The recruit's candidacy term to become a formal GSDF member was set to expire on June 27 but has been extended for three months, Defense Minister Yasukazu Hamada said Tuesday, explaining that the move was to allow the ministry to continue its investigations into the incident.