How protesters pulled off that stunt at U.S. Bank Stadium

How did they get all the way up there?

Some people are worried about the security at U.S. Bank Stadium after protestors climbed dang near to the roof to hang a sign.

But officials say they know how the protestors managed to carry out the stunt, and they're taking steps to make sure it doesn't happen again.

Three people were arrested Sunday after two of them dangled from the rafters and lowered a banner to protest the Dakota Access Pipeline – specifically, U.S. Bank's alleged financial involvement with the company building it.

So how did they get inside in the first place, and then get all the way up there? Well, first – they bought tickets.

"Our investigation shows these individuals properly entered the stadium as ticketed guests through our gates," SMG, a managing partner of the stadium, said in a news release Tuesday.

They made it through security with their gear – nylon rope, a small number of carabiners and a lightweight banner – hidden under winter coats, the release says. Then they climbed "regulation standard" barriers meant to block people from getting access to that area of the building.

SMG provided a photo of the barriers:

There was “nothing visible” on the protestors that violated stadium policies or prevented them from clearing the security screening when they entered the building, SMG added.

They also released a photo of two of the protesters outside the stadium on the plaza.

Changes will be made

Officials took "immediate steps to implement design changes" to the guard rails to prevent anyone from climbing over them again, the release says, and more changes will be made as the company evaluates new ways to beef up the security.

"Safety of all U.S. Bank Stadium guests continues to be the primary concern of all stadium partners including the MSFA, Vikings, SMG and Monterrey Security. We will continue to work together with the Minneapolis Police Department to further investigate this situation," the release states.

Officials also said they plan to prosecute the protestors "to the fullest extent of the law."