Senior gardaí confirmed, however, that 55-year-old Jim Hourigan could still face a charge of reckless endangerment.
His home-made bomb was elaborate, gardaí said, but it was not capable of being activated.
During the 29-hour stand-off this week, the centre of the north Tipperary town was cordoned off.
He threatened to explode eight large gas cylinders he had brought into his rented house at Rosemary St with a container of petrol.
After voluntarily going to Roscrea Garda Station, he agreed to voluntarily admit himself to St Michael’s hospital where he is still being treated.
A senior garda source said the incident remains under investigation.
Mr Hourigan, through his legal adviser, said he took his action to highlight a grievance he had with another solicitor over the manner in which he handled a civil action he was taking for sexual abuse.
A Christian Brother was jailed in 2003 for sexually assaulting Mr Hourigan, when he was training for the order in Dun Laoghaire.
The abuse went on over a two-year period after Mr Hourigan entered the college in 1964, aged 13.
A garda spokesman said they found eight large gas cylinders and a container of petrol in the house on Thursday night after Mr Hourigan left the building.
One garda source said: “It seemed a very elaborate set-up with wires and clocks attached to the cylinders. But it was not capable of being activated.
“However, if he started a fire with the petrol and the cylinders of gas went up, it could have caused huge destruction.”
There was a small amount of petrol spilt near the front door but the building had not been doused in fuel as Mr Hourigan told a number of journalists by phone during the stand-off.
Mr Hourigan, a qualified electrician, was arrested by gardaí last Monday in Roscrea and brought to Roxboro Road Garda Station in Limerick where he was questioned about an alleged threat he made against a solicitor who had been dealing with his civil action.
Another solicitor Joseph Burke of McCartan & Burke Solicitors, Dublin, was assigned to Mr Hourigan during the siege, with his agreement.
Mr Burke read out a statement to media two hours before Mr Hourigan ended the stand-off, which said he had been increasingly frustrated by the delays in achieving justice.
It is believed that gardaí were advised by a doctor that Mr Hourigan had been failing to take medication for a number of days prior to the incident in Roscrea.