A man was threatened with a handgun in Emerton on Sunday night.
Four men, one armed with a handgun, confronted a man, 18, in the front yard of a home in Emert Parade shortly before 6pm.
He was threatened before another man assaulted him.
Police said several of his friends were also assaulted before the four men ran to a Holden Commodore and drove away.
The armed man was described as being in his 20s, about 188cm tall, with a slim build and dark hair and wearing a grey hoodie and black track pants.
Police appealed to anyone with information to contact Mount Druitt detectives.
A girl was approached by a man driving a van in Rooty Hill on Tuesday of last week.
The girl, 15, said she was walking along Hartington Street about 7.15am when the van stopped next to her and the driver leaned out of the window and spoke to her.
The girl ran away and reported what had happened to teachers at her school on Wednesday.
They contacted police, who say they want to speak to a man described as being of South American appearance, 30 to 40 years of age and wearing work pants and a high-visibility work shirt.
Police urged anyone who had any information about this to contact Mount Druitt detectives on 9675 0699.
Police also urged parents to advise their children not to speak to people they did not know and to always inform their parents or teachers if such an incident occurred.
If approached, children should seek safety at a school, shop or service station and call their parents or police.
Car park stabbing
A man was stabbed in Shepherd Street, Colyton, on Monday night of last week. Police said the man, 25, was standing outside his vehicle in a car park about 8.50pm. Two men approached him and an argument followed. One of them struck him in the neck with an object, causing a deep cut. Anyone with any information is urged to contact St Marys detectives on 9677 7501.
Detectives from the Sex Crime Squad's Child Exploitation Internet Unit charged a Blackett man, 18, on Thursday with possessing child pornography.
Detectives who searched the man's home said they found a number of laptop computers and data storage devices and arrested the man. He was later charged with using a service for child pornography and was bailed to appear in Parramatta Local Court on June 18.
Police say they found drugs and knuckle-dusters in a car while patrolling a car park in Colyton last Friday, about 6.20pm. A Plumpton man, 37, will appear before Mount Druitt Local Court on June 9 charged with drug and property offences.