Exegesis:

parēsan de tines en autō tō kairō ‘at that very time some people came up,’ or, ‘were present,’ preferably the former. kairos means here ‘moment of time’ without the theological implications it has in 12.56.

apaggellontes autō peri tōn Galilaiōn ‘telling him about the Galileans,’ denoting the purpose of their coming. As shown by the article ton the clause refers to a commonly known fact. For apaggellō cf. on 7.18.

hōn to haima Pilatos emixen meta tōn thusiōn autōn ‘whose blood Pilate had mixed with (the blood of) their sacrifices,’ with tou haimatos understood after meta. The reference is to people who were killed by Roman soldiers when they were slaughtering the beasts they had brought as sacrifices. The phrase ‘to mix blood with blood’ is a Hebraism. thusia (cf. on 2.24) refers here to sacrificial animals.

Translation:

At that very time, i.e. in the same point of time, ‘at the same occasion.’

Told him of the Galileans whose …, or, ‘told Jesus about (or, the story of) the G. whose…,’ ‘told Jesus that there were G. whose…’ (or in direct discourse).

The Galileans whose blood Pilate had mingled with their sacrifices. The clause structure often has to be changed, cf. e.g. ‘the G. whose blood had-been-shed by P., so-that it got-mixed with their sacrifices’ (Batak Toba), or, making explicit the function of the Hebraistic expression, ‘there-are G. killed by P…, mixed-together (is) their blood and the blood of the animals they slaughtered’ (Tae’ 1933), or again, substituting the function, ‘the G. whom P. killed while they were sacrificing’ (Dan, cf. Good News Translation). Galileans, i.e. men from the land Galilee, and see below on 22.59. Sacrifices, or, ‘animals they had slaughtered (in the temple), or, killed as a gift (for God)’; and cf. 2.24. Pilate. For a title, if required with the name, cf. “governor” on 2.2.

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.