A fast leak can involve water control, building safety, cleanup, and pipe repair at the same time.
The short answer
If it is safe and you know the correct main shutoff, stop the supply. Keep away from electrical hazards and weakened ceilings or floors. A suspected burst needs prompt professional attention, but the visible opening may not be the only damaged section. Do not promise a cause before the piping is examined.
What to notice
Give the call a timeline
Record when full pressure was last normal, when water first appeared, and any recent freeze, impact, or work nearby. State whether the house supply is off and whether water continues from stored or upper-level lines. Mention the pipe material only if you can identify it reliably; a guess can send the wrong repair assumption.
Plan for access and residual water
Explain whether the pipe is exposed, behind a finish, above a ceiling, or near equipment. Water can remain in cavities after the supply stops. Ask how the repair area will be reached and who handles drying, material removal, and restoration. Protecting the home is not identical to replacing the failed section.
Ask why the section failed
After control is restored, ask what evidence supports the cause and whether adjacent piping needs observation. A freeze-related break, a failed connection, damage, and deterioration can imply different follow-up. Avoid authorizing broad replacement solely from a dramatic symptom without a documented scope and explanation.
One useful question
Does shutting off the main end the problem?
It can stop new supply water, but it does not remove water already in piping or building materials. It also does not establish the cause or make wet electrical and structural areas safe. Ask the appropriate qualified people to evaluate those separate concerns.