A 16-year-old boy who is being questioned over the stabbing of an army chaplain, had been reposting propaganda from Islamist terrorist organisations after being radicalised online, gardaí have established.

The Irish Independent has learned he had come to the attention of specialist gardaí and was being monitored before Thursday night’s attack at a barracks in Galway because of the “open nature” of what the teenager was posting online.

Within hours of chaplain Fr Paul Murphy (52) being attacked at 10.45pm on Thursday with a large bayonet-style knife at Renmore Barracks, detectives raided the family home of the boy and seized a number of devices including his laptop and mobile phones.

The Special Detective Unit, which investigates terror offences, as well as computer specialists in the Garda Cyber Crime Unit, is now heavily involved in the investigation and is analysing the seized electronic equipment.

“The expectation is that more incriminating evidence will be found on these devices, but gardaí are aware that this individual had been reposting fairly disturbing material from organisations affiliated with terror groups such as Isis (IS) and Al-Qa’ida in recent months,” a source said.

“He was doing this openly and regularly online while using his own name – the belief is that he got radicalised himself within the course of the past year, possibly by getting involved in internet group chats.”

It can be revealed that the ­teenager was particularly “obsessed” about the Islamist insurrection in the African country of Mali that is being led by ­Al-Qa’ida-backed militants.

The Defence Forces had been deployed to Mali for almost 10 years where they were involved in training and peacekeeping as well as counter-terrorism missions before pulling out of the war-torn country last September.

“The Irish Army’s previous presence in Mali seems to have fixated the suspect for some reason and while carrying out the knife attack on Thursday night, he made a number of comments about Mali,” added the source.

“Some of what he said at the scene of the assault as well as his internet history is forming a big part of the terrorism investigation.”

Detectives have uncovered no ­evidence that the teenager had ­posted any previous threats against the Defence Forces and all the current information is that he acted as a “lone wolf”.

“There is no evidence yet that he has recruited anyone and there is nothing at all to suggest that there is a radical terror cell operating in Galway,” the source said. “There is also no evidence that he was in direct contact with anyone from the Islamist terror groups.”

The teenager had been living in the Galway city area with his family, who originally came to the country from the UK.

“He had been radicalised relatively recently, but there can be no doubt that he was showing open support online to Islamist terrorist organisations,” the source said.

“He was reposting this material ­rather than generating it himself.”

It is expected that Fr Murphy will recover from his injuries. He had surgery yesterday in hospital after suffering stab wounds to his arms.

Before his surgery, the chaplain reassured his parish and friends in a Facebook message that he was OK.

Originally from Co Waterford, Fr Murphy has been a chaplain in the Defence Forces for decades and has served on a number of overseas missions.

He was initially stabbed as he sat in his car when he pulled up at the gates of Renmore Barracks, waiting for the gate to open. The car drove through the gate as the teenager allegedly continued the attack. ​

Members of the Defence Forces fired a number of warning shots in an attempt to prevent the teenage suspect from further injuring the chaplain.

A car wrapped in plastic at the scene of the attack at Renmore Barracks in Galway. Photo: PA

Five shots were fired in the air before up to three Defence Forces personnel wrestled the suspect to the ground and detained him before the gardaí’s Armed Support Unit arrived at the scene a short time later.

A Defence Forces spokesman said: “Upon witnessing the assault, the soldiers on duty responded swiftly and appropriately to the immediate threat, using necessary force to ensure the safety of all personnel and to secure the area.

“This included the firing of live ammunition as warning shots.

“The assailant was promptly detained and handed over to An Garda Síochána upon their arrival, and a full investigation into the incident is now being conducted by An Garda Síochána”

The suspect continued to be questioned last night by gardaí who are investigating both the stab attack as well as potential serious terrorist charges.

Taoiseach Simon Harris said he had been briefed on the “shocking” incident and his thoughts were with Fr Murphy.

“I want to thank the Defence Forces personnel and gardaí for their action and response,” he said.