As noted earlier, it looked like a fan rushed the ring on Monday Night Raw and was then tackled by security.
According to several reports at the arena, that fan was actually the pastor that was scheduled to be in the following segment with Bobby Lashley and Lana.
As you can see in the video, he ran into the ring right after AJ Styles finished celebrating his win over Akira Tozawa. Security, apparently not realizing who the guy was, sprung into action to take him down. It looked like someone did not give the security a heads up. One of the WWE cameramen captured the moment just as they were about to go to commercial break.
You can see a clip of what happened by clicking below.