Police investigating an arson attack on a church in Londonderry have said they believe two males may have started the fire.
The fire happened at Holy Family Church in Ballymagroarty shortly after 22:00 BST on Friday night.
The fire service said CCTV showed the fire had been started deliberately by several youths.
Parish priest Fr Paddy O'Kane was visiting a sick man whose son showed him a photograph of the fire.
He thought at first it was "trick photography".
"I thought he was playing a joke," he said.
"I went to the front of the man's house and then I could see smoke rising. The community had gathered. I got a terrible shock."
The parochial house of the church was evacuated and 20 firefighters tackled the blaze.
Fr O'Kane said he had not been allowed back into the building while forensics officers worked on the scene.
Fr O'Kane said he could not understand the motivation of the young men behind the arson attack, but he would pray for them at weekend masses.
"I never can understand vandalism or arson, I don't understand what buzz it gives people," he said.
"I can't understand what goes on in a person's mind that they want to cause damage to other people and how it can make them feel good.
"I feel more sorry for them. There is something badly wrong in their lives whenever they do this."
Group Commander Andy Burns said it had put lives in danger and that a community event was being held in the parochial house when the blaze broke out.
He said the fire was started in a shed to the rear of the parochial house.
The house was damaged, with the heat destroying windows.
'People can lose their lives'
The fire also spread to the church roof and tiles were removed by the fire service to prevent it spreading further, he said.
The CCTV footage had been passed to police for investigation, Group Cmdr Burns added.
"This was arson. This had the potential to spread to the adjoining parochial house, which was occupied, and people can lose their lives in this type of incident," he said.
"We would ask our young people, please do not get involved in setting deliberate fires, setting fires like this is very dangerous."
PSNI Det Con Fielding said: "At this stage we believe two males may have been involved in starting this fire and we are keen to identify them.
"We would like to hear from anyone who was in the area at around the time of the fire or anyone who may have information regarding this crime."
Sinn Féin councillor Michael Cooper condemned the attack: "The mindset of actually going down and deliberately setting fire to a church or any community building defies logic.
"This has caused extreme anger and disbelief in the community who go to this chapel."
SDLP councillor Shauna Cusack described it as a "reckless act".
"I don't know what they were trying to achieve - it put people at risk.
"It also put the fire service at risk too. I really can't understand the mindset of people who would want to destroy a place of worship and somebody's home."