Charlie Kirk shooting suspect Tyler Robinson used President Donald Trump’s name as a pseudonym on Valve Corp’s Steam video game platform, a fact that has become part of a profile US law enforcement is building on the alleged assailant. The US Secret Service has joined the investigation into the shooting, even though Mr Kirk was not under the agency’s protection, according to the people with knowledge of the matter. Agents are working with the Federal Bureau of Investigation to study Robinson’s behaviour and online activity, including his use of Mr Trump’s name on Steam, as part of a profile they...