The fan, wearing a device that let out a pink smoke, ran across the field just before halftime before Wagner laid a big hit, which was initially shared by Cameron Salerno of the Sacramento Bee in a Twitter video.
"That's not making a play," Wagner said after the game via ESPN. "That's just keeping it safe. You don't know what that fan got or what they're doing. You see it all the time, and we don't know what they're carrying in their pockets. It's whatever that little smoke stuff is, but that s--- could be dangerous.
"One of the guys on the other side, it looked like he got hurt, and security looked like he was struggling, so I was frustrated, so I took it out on him."
The run was initially hidden from ESPN's main Monday Night Football broadcast, however, ESPN2 showed a clip of Wagner's hit seconds later during the ManningCast with Peyton and Eli Manning, which was broken down by the two legendary quarterbacks.
Wagner recorded a team-best 10 tackles during Monday's (October 3) loss to the 49ers.
The Los Angeles native signed a five-year, $50 million deal with the Rams during the offseason after spending his entire NFL career with the Seattle Seahawks.
Wagner, 31, has been selected to the Pro Bowl during every season since 2014 and is a six-time first-team All-Pro (2014, 2016-20) and two-time second-team All-Pro (2015, 2021).