Longtime concert-goer Julianna Zyra was with her partner near the disability tent at Boston Calling’s concert on Sunday when she saw someone pass out, and she ran to get help.

“It took them probably like 5-plus minutes to get to this person that had passed out in the middle of this crowd,” she said.

She said others saw people fainting and having seizures during the hot Sunday Hozier performance, and it took a while for medical staff to get to them.

The Boston Calling festival was plagued with complaints of overcrowding, difficulties getting water, long bathroom lines, and people having medical issues with little easy access to medical personnel. There were about 800 medical encounters with Boston EMS, and 23 people treated and sent to area hospitals, with the majority happening on Sunday, according to a Boston EMS spokesperson. They said most of those encounters were minor first aid requests, including giving out bandages, providing Tylenol and treating heat-related illness. On Sunday, 412 people were assisted, and 13 went to area hospitals.

Boston Calling organizers told GBH in a statement that they want to “acknowledge feedback from Sunday.”

“While attendee count was several thousand below the official capacity rating of the site, we never want anyone to feel uncomfortable or unsafe at the show,” said Boston Calling, calling safety and well-being “paramount.” The organization didn’t respond to a request for crowd counts, but several interviewees told GBH News that staff had told them 30,000 single day tickets were sold for Sunday.

Reneé Rapp on Friday and The Killers on Sunday both stopped their sets to direct EMTs to medical emergencies, according to several concert-goers who witnessed the incidents and spoke to GBH.

It was Anissa Mansour’s first Boston Calling. Mansour said she heard people yelling and screaming for help on Sunday, calling it “intense.”

“I saw three people in my vicinity faint. And then there was a couple times where I just saw security and EMTs running behind me,” she said. “I witnessed three people pass out, and then one person was hauled out on a stretcher.”

Volunteer and longtime concert-goer Saffron Donovan was stuck in the crowd between Megan Thee Stallion and Hozier on Sunday.

“At one point, I was literally my chest and my back were crushed between two strangers. And nobody could move. Everybody was pushing and shoving and screaming like, 'Let us move, let us move. We want to get out!’” Donovan said. “It was pretty chaotic and pretty scary, honestly.”

She said she didn’t see a single security personnel providing help in that vicinity, and many in the crowd were trying to help each other.

Multiple sources told GBH News that due to the crowding, disabled attendees were forced outside of accessible viewing areas. Some said they saw service animals nearly be trampled.

The crowding and setup also made finding a bathroom difficult.

“I was told as a companion to someone in ADA [Americans with Disabilities Act], I wasn’t able to use the ADA bathroom, so I tried to go to one of the other bathrooms, which is like probably half a mile away, and it was basically a human barricade and you couldn’t get in,” Zyra said.

She also was concerned about the water situation on Sunday, saying that for many, the only option was to buy a canned beverage for at least $5.

Others described the free water stations as insufficient to meet demand, and too far away.

Joshua Dupaty, 26, said they were proactive in filling a 32-ounce water bottle upon arriving Sunday and again when there was a 20-minute line for the free water station in the afternoon. During the evening, the line was around an hour for free water, so they waited in line over 30 minutes to pay for a can at a concession stand.

“The difficulty in just getting water was absolutely ridiculous and if you weren’t extremely proactive — you could easily get dehydrated,” they said.

Dupaty left with friends early because of the crowding. So did Mansour, who hopes the organizers of the festival take notice of people’s concerns.

“I would hope that they saw what happened and, like, took the appropriate measures for the next time around — I think in terms of crowding and spacing and ticket sales,” Mansour said, adding that if that if organizers don’t make changes, she won’t go back.

Boston Calling organizers said in their statement that they “will to continue to work with public officials and our operations team to improve the experience, layout, and ultimately create a better environment for everyone.”