I was flying my Phantom 3 pro at around 150ft high when I noticed an approaching Fire Dept hellicopter heading toward the Phantom. Nothing happened but I assume I'm within the law right? He's supposed to get out of my way and not fly under 400ft right? I basically hovered until he flew passed me.

An occupied craft always has the right of way.   You are kidding.............................right?

Absolutely not, you have no rights in the presence of a manned aircraft, you must get down as quickly as possible.

Get down, with your bad self and boogie... Haha
We are the underdog of the flight world. And hey, our rights are to drop down and give them 10 push-ups... ;-)

RedHotPoker

You have to go down asap because you don't know if they are in duty.

"He's supposed to get out of my way and not fly under 400ft right? "

FYI .. here are the rules for real planes and helicopters in your part of the world regarding minimum safe altitudes.  Pay particular attention to the second half:

§ 91.119 Minimum safe altitudes: General.
Except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes:
(a) Anywhere. An altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface.
(b) Over congested areas. Over any congested area of a city, town, or settlement, or over any open air assembly of persons, an altitude of 1,000 feet above the highest obstacle within a horizontal radius of 2,000 feet of the aircraft.
(c) Over other than congested areas. An altitude of 500 feet above the surface, except over open water or sparsely populated areas. In those cases, the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure.
(d) Helicopters, powered parachutes, and weight-shift-control aircraft. If the operation is conducted without hazard to persons or property on the surface—
(1) A helicopter may be operated at less than the minimums prescribed in paragraph (b) or (c) of this section, provided each person operating the helicopter complies with any routes or altitudes specifically prescribed for helicopters by the FAA

1. no, not within the law>
2. the manned aircraft is supposed to DODGE you??? , yea what world is that!
3. He can fly ANYWHERE he wants/needs to. 400 is meaningless except to us ....