LONDON — Mourners wearing colorful Harry Potter scarves and Marvel superhero shirts were joined by the leaders of Britain and Ireland Wednesday at the funeral of Lyra McKee, the journalist shot dead during rioting in Northern Ireland last week.

U.K. Prime Minister Theresa May, Irish Prime Minister Leo Varadkar and Ireland's President, Michael D. Higgins, were among hundreds of people celebrating the life of a young woman whose death in paramilitary gunfire has shocked a region usually inured to violence.

U.K. Labour Party leader Jeremy Corbyn and the leaders of Northern Ireland's Catholic and Protestant political parties also attended the service at St. Anne's Cathedral in Belfast. Some of McKee's family and friends wore Harry Potter and Marvel items in tribute to her love of those fictional worlds.

Taoiseach Leo Varadkar, Britain's Prime Minister Theresa May and Ireland's President Michael D. Higgins attend the funeral service for murdered journalist Lyra McKee at St Anne's Cathedral in Belfast, Northern Ireland April 24, 2019. Brian Lawless / Reuters

McKee, 29, was killed Thursday as she reported on rioting in the city of Londonderry, also known as Derry.

She was the first journalist killed on the job in the U.K. for almost 20 years, and her death caused wide shock in Northern Ireland still shaken by tremors from decades of violence known as the "Troubles."

A small Irish nationalist militant group, the New IRA, said it was responsible. The group apologized, saying McKee was shot "while standing beside enemy forces" — a reference to the police.

Police arrested two teenagers and a 57-year-old woman but released all three without charge.

The IRA and most other paramilitary groups have disarmed since Northern Ireland's 1998 peace accord, but a small number of dissidents refused to abandon violence, and have targeted police and prison officials with bombings and shooting.

Mourners gather around a floral memorial for Lyra McKee after she was fatally shot two days earlier in Londonderry, Norther Ireland, on April 20, 2019. Paul Faith / AFP - Getty Images

The New IRA, the largest of the splinter groups opposed to the peace process, has been blamed for a January car bomb outside the main courthouse in Derry and claimed responsibility for a series of letter bombs sent to transit hubs in Britain last month. No one was injured in either attack.

McKee had written about growing up gay in Northern Ireland and the struggles of the "cease-fire babies," the generation raised after the 1998 Good Friday accord that ended three decades of sectarian conflict.

"We were the Good Friday Agreement generation, destined to never witness the horrors of war but to reap the spoils of peace. The spoils just never seemed to reach us," McKee wrote in 2016.

Security officials have warned that political drift in Northern Ireland and uncertainty around Brexit could embolden those bent on violence.

Northern Ireland's power-sharing government has been suspended for two years because of a dispute between the main Protestant and Catholic political parties.

The coffin of journalist Lyra McKee arrives at her funeral at St. Anne's Cathedral in Belfast, Northern Ireland April 24, 2019. Clodagh Kilcoyne / Reuters

The U.K.'s planned departure from the EU has revived fears of a return to border checks between Northern Ireland, which is part of the U.K., and EU member Ireland. Customs posts or other infrastructure along the 300-mile frontier would disrupt people and businesses on both sides and could become a target of attack.

Britain, the EU and Ireland all say there will be no hard border, but it remains unclear how that will be achieved.

In a statement released on the eve of the funeral, McKee's family remembered her as "a smart, strong-minded woman who believed passionately in inclusivity, justice and truth."

"We would ask that Lyra's life and her personal philosophy are used as an example to us all as we face this tragedy together," the family said. "Lyra's answer would have been simple: the only way to overcome hatred and intolerance is with love, understanding and kindness."