POLICE had a "significant" operation in place in Derry's Galliagh when two masked men fired shots in the air at a commemoration for INLA hunger striker Michael Devine.
Unionist politicians reacted angrily when video footage was posted on social media.
The commemoration at Fern Park in Derry took place on Friday night to mark the fortieth anniversary.
A group of masked men walked to a mural in memory of Devine, the final 1981 hunger striker to die. Two members fired shots into the air before the grouped walked away.
It has now emerged that police believed there was a possibility of the anniversary being marked by a show of strength. PSNI superintendent Catherine Magee said police believed something was planned based on previous experience.
In May, shots were fired in the air by masked men at a commemoration in the Bishop Street area, marking the death of hunger striker Patsy O'Hara.
Ms Magee said: “Because my working assumption was that there might be a possibility that there may be an intent to do this, I had a significant policing operation in place and I had local neighbourhood police officers who routinely patrol Galliagh every day of the week, they were out on the ground engaging with local residents and providing high visibility local support as they always do.”
In an interview with BBC radio, she added that tactical support units were also patrolling the area. Police were aware of the commemoration and were trying to strike a balance so that all needs could be met.
She added that the entire incident lasted between 30 seconds and one minute and up to 10 shots were fired.
"The police were in Galliagh; we were in the main arterial routes in Galliagh. We weren’t on top of the commemoration event that was happening as you might imagine. That in itself may create community tension but we were directly in the area and community engagement with police was positive all night.”
She said the PSNI would follow up the incident with a “strong and robust criminal justice strategy”.
