Tight security was observed as delegates arrived for the Republican National Convention in Milwaukee on Monday, where the nominees for president and vice president will be selected.

"A lot of momentum going into this. I just keep an open mind. What's going to happen is going to happen. We're more united than ever. Easy," an attendee said.

Footage shows police officers guarding entrances as attendees entered the convention grounds.

"We were just saddened by that day. But this convention has put a renewed life in everybody, as if we weren't already excited about president Trump, we're more excited about it now. And our word is 'determined'," another attendee added.

Around 2,500 delegates gather in Milwaukee for the event. At the time of publication Donald Trump was elected presidential nominee and picked Senator JD Vance of Ohio as his vice presidential nomination.

The convention will mark the former president's first live appearance since the failed assassination attempt at his campaign rally in Butler, Pennsylvania, where he was lightly wounded while a spectator was killed.

Trump was shot to his right ear when he was delivering his speech in the rally in Butler, Pennsylvania on Saturday. As rows of shots fired, the candidate ducked behind his lectern and was surrounded by bodyguards before being taken out of the venue, while raising his fist into the air.

The alleged gunman was killed by the US Secret Service agents. Another attendee was also reported dead in the rally, with two others in critical condition.

Following the incident, President Joe Biden made his statements in a speech in Rehoboth Beach, calling it 'sick' and condemning the violent act.

Other US politicians like former president Barack Obama and Secretary of States Antony Blinken also commented on the shooting, condemning political violence and sending wishes to Trump.

The case is currently being investigated as a possible assassination attempt, according to law enforcement officials.