What constitutes heat of passion in a murder case?

Thus, heat of passion arises if, " 'at the time of the killing, the reason of the accused was obscured or disturbed by passion to such an extent as would cause the ordinarily reasonable person of average disposition to act rashly and without deliberation and reflection, and from such passion rather than from judgment.' " (People v. Barton, supra, 12 Cal.4th at p. 201.) "Heat of passion, then, is a state of mind caused by legally sufficient provocation that causes a person to act, not out of rational thought but out of unconsidered reaction to the provocation. While some measure of thought is required to form either an intent to kill or a conscious disregard for human life, a person who acts without reflection in response to adequate provocation does not act with malice." (People v. Beltran (2013) 56 Cal.4th 935, 942 (Beltran))