Paul Eason said he was "not aware of a crush and nobody seemed to be responding as if there was one"
A senior ambulance officer at Hillsborough told a jury he may have "panicked" and "froze" on the day of the disaster.
Inquests heard emergency services lost "valuable minutes" due to a "flawed" assessment by Paul Eason.
Mr Eason, who said he was the ambulance service's "eyes and ears" in the Sheffield stadium, admitted he had not seen fans being crushed.
His "biggest mistake" was assuming the crowd behaviour was to blame, he said.
New inquests are being held over the deaths of 96 Liverpool fans fatally crushed at Sheffield Wednesday's ground during the FA Cup semi-final against Nottingham Forest on 15 April 1989.
Mr Eason, who was at the ground with three colleagues, said part of his job was to liaise with the club and be the ambulance service's "eyes and ears".
The jury was shown footage of Mr Eason and colleague Stephen Chippendale heading to the Leppings Lane terraces at about 15:04 BST.
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He told the court the crowd had appeared "volatile" and he was punched in the chest, but did not speak to anyone about what was happening.
Mr Eason agreed he should have spoken to the police and St John Ambulance and he should have looked into the pens themselves.
He said he had not declared a "major incident" until 15:22, which he agreed was "far too late".
Asking about the situation on the terraces, Jo Delahunty QC, who represents a group of victims' families, said: "Are you seriously telling this jury that at that point you did not have an idea what situation the people behind that pen were placed in?"
Mr Eason said he was and he had "no need to lie to the jury".
'Crowd disturbance'
After showing footage of the Leppings Lane end timed at 15:08, Ms Delahunty said to Mr Eason: "My suggestion to you is whilst you might have been frozen in fear initially, you were now under a professional duty to react and to act and this is what you singularly failed to do throughout the entirety of the rest of the time you were on the pitch."
Mr Eason did not reply to this.
He said he and Mr Chippendale then began treating a man with a suspected broken leg on the pitch, who he believed was their "priority", before going to fetch some equipment from an ambulance.
He said as he walked back to the ambulance, he "rightly or wrongly, had made an impression that there had been some sort of crowd problem".
That opinion was not based on anything anybody had told him or on "having a view in to the pens", he said.
"I think at the time, there were a lot of problems with fans' behaviour and I think I made the mistake of deciding this match had been one of those occasions."
Paul Eason said he may have "panicked" and "froze" during the disaster
He said he was not aware of a crush and nobody around him seemed to be responding as if there was one.
"I think, looking back in hindsight, the assessment is flawed," he said.
"I think the biggest mistake was presuming it was something it was not.
"I think taking cues from police officers and other people who didn't appear to be concerned was, again, wrong."
Mr Eason said when he returned to the Leppings Lane end after 15:10, the crowd was "a lot more angry" and there were many more injured spectators.
'I'm human'
He said he had still thought it was a "crowd disturbance" and felt "very, very concerned and desperate to get some sort of help - I felt very alone".
He agreed that "valuable minutes were lost" and that he may have "panicked" and "froze".
"I think that's quite possible. I'm a human being," he said.
"If I panicked, I'm still trying to function and do something.
"I think it's quite possible that the enormity of it all is starting to dawn on me and I might have been overwhelmed."
"What I do think is that under extreme circumstances, we all did the best that we could."
The inquests, held in Warrington, continue.
