Reaction is pouring in online after at least 50 people were killed and another 53 people were injured in a mass shooting at a gay nightclub in Orlando, Fla. Officials say the attack is the worst mass shooting in U.S. history

Here is a look at some of the reaction.

WHITE HOUSE

HILLARY CLINTON

DONALD TRUMP

Officials across Florida expressed their condolences online. Orlando Police shared the story of an officer nearly killed in the gunfire and Equality Florida, an advocacy group, underlined the role gay clubs have held as safe spaces for the LGBTQ community.

FLORIDA GOVERNOR RICK SCOTT

EQUALITY FLORIDA

ORLANDO POLICE

A call for blood donations led to massive crowds at donor centres, but some expressed outrage at the fact that gay men are banned from donating blood due to U.S. FDA regulations.

ONE BLOOD

FLORIDA STATE SENATOR DARREN SOTO

Canadian politicians from all levels of government offered words of support.

PRIME MINISTER JUSTIN TRUDEAU

MINISTER OF PUBLIC SAFETY RALPH GOODALE

MINISTER OF NATIONAL DEFENCE HAJIT SAJJAN

CONSERVATIVE INTERIM LEADER RONA AMBROSE

NDP LEADER TOM MULCAIR

ONTARIO PREMIER KATHLEEN WYNNE

LIBERAL MP ROB OLIPHANT

The mass shooting at Pulse nightclub comes as Canada and the U.S. celebrate Pride month. Vigils across Canada have been organized to honour those killed in the Orlando massacre.

PRIDE TORONTO

Celebrities, politicians and leaders within the gay community also expressed messages of grief and outrage.

CHER

JULIANNE MOORE

MICHELLE VISAGE

ARIANA GRANDE

MAYOR OF LONDON SADIQ KHAN

ELLEN DEGENERES

LAVERNE COX