WASHINGTON (Reuters) - The Secret Service is investigating an incident at presidential candidate Donald Trump’s rally in Radford, Virginia in which an agent shoved a Time magazine photographer to the ground, an agency spokesman said on Tuesday. “We are investigating the matter fully to find out what our employee did and what the other person did,” Kevin Dye told Reuters.  Video footage of the altercation on Monday, which was posted on the Internet, shows Time magazine photographer Christopher Morris getting close to the agent, who threw him to the ground and Morris kicking the agent from the floor. The magazine said Morris was knocked to the ground after stepping out of the press hold to take a picture of protesters. A Trump campaign spokeswoman acknowledged the incident, but said the campaign was not aware of the details. In a statement published in Time, Morris said he had covered the White House for nine years without altercations with the Secret Service. “The rules at Trump events are significantly stricter than other campaigns and make it very difficult to work as a photographer, as many others have pointed out before me,” Morris said. “I regret my role in the confrontation, but the agent’s response was disproportionate and unnecessarily violent.” Free speech advocates have decried Trump’s treatment of protesters and reporters at his rallies, including ushering out dissenters and shouting at the press.   The Secret Service said it would never intervene to quiet protesters or restrict journalists unless there was a public safety matter.  “The Secret Service’s role is to protect the candidate and the public,” Dye said. “(Agents are) not in any way responsible for removing protesters. We have a strong commitment to upholding the First Amendment.” Trump and Ben Carson are the only two Republican presidential contenders to receive Secret Service protection, along with Democratic contenders Hillary Clinton and Bernie Sanders. Candidates must request the coverage.  White House spokesman Josh Earnest on Tuesday acknowledged that the Secret Service has indicated it would “look at this particular situation.” 