In Mordenkainen's Tome of Foes (p. 129), the Deathlock Mastermind has the following attack:
Grave Bolts. Ranged Spell Attack: +6 to hit, range 120 ft., one or two targets. Hit: 18 (4d8) necrotic damage.
Can the Mastermind attack one creature with two bolts in a single round? Or is this specifically different from multiattack so that the Mastermind gets the benefit of multiple attacks if multiple targets are present?