Homicide squad Detective Inspector Andrew Stamper said extreme violence was inflicted on Ms Herron and it's not known if there was one or more attackers.
"The level of violence involved here was extreme in my view," he told reporters on Sunday.
"This was a particularly, particularly horrendous attack."
Investigators believe Ms Herron was bashed just hours before her body was found about 9.25am on Saturday by dog walkers.
Insp. Stamper said the attacker did try and conceal the body and there was no evidence as yet that it was a sexually motivated crime or if a weapon was used.
Ms Herron had been couch surfing and sleeping rough for some time while struggling with drug and mental health issues, Insp. Stamper said.
The last confirmed sighting of her was on May 14 at St Albans when she came into contact with the police.
Her family have been told of her death.
Police want to hear from anyone who might have information.
"We've spoken to a number of rough sleepers who were in that area at the time," Insp. Stamper said.
"They have been helpful with us in building that picture.
"There's still a lot of gaps in terms of what actually happened in the park. So we need information from the public in terms of times, if they have seen something, that will enable us to sort of narrow down a lot of our inquiries and focus on, you know, whether it be CCTV, public transport, as I say, these are all issues in play at the moment."
Ms Herron's death has again sparked anger in Melbourne, with police and the premier calling for men's attitudes to women to change.
"This is a terrible tragedy," Premier Daniel Andrews told reporters on Sunday.
The premier, who delivered Australia's first royal commission into family violence last term, said while the state had made significant progress on violence against women, there was more to be done.
"This is not about the way women behave, this is not about where women are at what hour," he said.
"This is most likely about the behaviour of men."
Insp. Stamper said he was "angry" when these crimes occur.
"I'm a father of a daughter, and you know, so, I feel it just the same as everyone else, when it happens," he said..
Members of the public have started to lay floral tributes at the site where Ms Herron's body was found, which is a short distance from Princes Park, where aspiring comedian Eurydice Dixon's body was found on June 12 last year.
The death is the latest in a series of women killed and dumped on Melbourne's streets since Ms Dixon's rape and murder.
Aiia Maasarwe, 21, suffered a similar fate to Ms Dixon after being attacked on her walk home near La Trobe University on January 15.
Both women were attacked by men they did not know and who have since been charged.
In April Natalina Angok's body was found dumped in Chinatown, allegedly killed by her one-time partner Christopher Allen who has been charged.
