Washington, Utah, located just south-west of Zion National Park, is surrounded by cinematic, flat-topped mountains and has long been a hub for exploring the natural wonders of the American west.

Yet, the last 48 hours have left residents wondering how the portal to the most beautiful parts of the country may have produced one of its ugliest acts of political violence in years.

Tyler Robinson, the man authorities accused of killing the conservative activist Charlie Kirk at Utah Valley University this week, resided in the area, according to police. He is now in custody after his father apparently persuaded him to surrender.

Local and federal law enforcement officers descended on typically quiet blocks in Washington and nearby St George, banging on doors and closing off streets as they carried out a high-stakes investigation.

Outside the Robinson family home in Washington, neighbours expressed shock that a fellow resident could have committed such an attack.

It shakes up a community because you don't expect it, said Addi Jacobson, 20, who recently moved into her grandmother's house in the neighbourhood.

Ms Jacobson said she did not personally know the Robinson family, but her grandmother did. She just was saying that she thinks that, from what she's seen and what she knows, they're a great family, just regular citizens, Ms Jacobson said. She used the words, 'very patriotic people'.

The night before Mr Robinson's arrest, police vehicles descended on a townhouse complex in St George - about 10 minutes from Washington - where local media reported the suspect had an apartment.

Utah County Attorney Jeff Gray plans to file formal charges against Mr Robinson on Tuesday. The nation, including the current occupants of the White House, will be watching.

This whole time, I never knew that I was living next to somebody capable of something like this, Ms Jacobson said as she played in the park with her fiancé and baby. It just makes you kind of question 'how much closer am I to somebody else that could be this way?'