Authorities in Northern Ireland released two teenagers arrested in connection with last week’s fatal shooting of journalist Lyra McKee, police said Sunday.

The two unidentified men, ages 18 and 19, were set free without charge after their arrest Saturday, the Police Service of Northern Ireland said in a statement.

Detective Superintendent Jason Murphy pleaded for witnesses with cell phone footage to come forward, saying in the statement, “I know there will be some people who know what happened but are scared to come forward but if you have information, no matter how small, please contact detectives.”

McKee, 29, had been reporting on a riot in the city of Londonderry on Thursday when she was shot dead.

Journalist and author Lyra McKee on May 19, 2017. Jess Lowe / via AFP - Getty Images

Authorities have described the killing as a “terrorist act” and said a dissident paramilitary group called the New Irish Republican Army was likely responsible.

The group has rejected the 1998 peace agreement between Britain and Ireland that ended decades of deadly violence during “The Troubles.”

McKee, who rose to prominence with a 2014 essay about her struggle growing up gay in Belfast, was described by a colleague as “rising star.” Her first book, “Lost Boys,” was to be published next year.