Image copyright AP Image caption Army Specialist Ivan Lopez was reportedly being assessed for post-traumatic stress disorder

A soldier who killed three men at a US Army base on Wednesday had an argument over a request for leave shortly before the shooting, reports say.

Specialist Ivan Lopez, 34, was denied leave to attend to family matters, officials speaking on condition of anonymity told US media.

He also wounded 16 people before shooting himself at the Fort Hood base.

The soldier's father said on Friday he "could not have been in his right frame of mind" during the attack.

Spc Lopez is alleged to have walked into one of the buildings of the Fort Hood base and opened fire with a .45-calibre semi-automatic pistol.

He then got into a vehicle and continued firing before entering another building and opening fire again. He was eventually stopped by military police, shooting himself in the head when confronted by a female officer in the car park, officials say.

'Agitated and disrespectful'

The New York Times, quoting an unnamed official, said Spc Lopez was agitated and disrespectful when his request for leave was denied.

He had reportedly sought time off to deal with family matters relating to the recent death of his mother.

An Army spokesman declined to comment on the nature of the argument but confirmed that the soldier had become angry with other members of his unit before the attack. Two of those killed belonged to his unit.

However, he added there was still "no concrete motive" for the attack and it might never be known why the shooting had taken place.

Officials have previously confirmed that Spc Lopez was being treated for depression and anxiety.

He was also undergoing evaluation for post-traumatic stress disorder following service in Iraq.

The dead men were formally named on Friday as Sgt First Class Daniel Ferguson, 39, Staff Sgt Carlos Lazaney-Rodriguez, who was 38, and 37-year-old Army Sgt Timothy Owens.

Media playback is unsupported on your device Media caption The communities around Fort Hood have been flying flags at half-mast, as Nick Bryant reports

Fort Hood was also the scene of a gun rampage in 2009 that left 13 soldiers dead and 32 wounded.

Maj Nidal Hasan was sentenced to death last September for that shooting.

It was the deadliest attack on a domestic military installation in US history.

The building where it occurred has only recently been demolished to make way for a place of remembrance.

Another US soldier, Muslim convert Naser Jason Abdo, was jailed for life for plotting to blow up a restaurant full of troops near Fort Hood in 2011.